Quantifying the Time-Variation in FRF Measurements Using Random Phase Multisines With Nonuniformly Spaced Harmonics

Recently methods have been developed to detect and quantify the influence of time-variation in frequency response function measurements using random excitations. These methods can also be applied to random phase multisine excitations, provided uniformly spaced excited harmonics. However, in quite a few applications, a nonuniform harmonic spacing is required, for example, a quasi-logarithmic spacing to cover a large frequency range, and a random spacing to detect and quantify nonlinear distortions. Therefore, in this paper, the results are extended to random phase multisines with nonuniformly spaced harmonics. An in-depth study of the noise sensitivity (bias and variance) of the proposed procedure is made.